The Ernemen snatched a shock victory with a late goal through Ryan Keenan to win by a point – on a scoreline of 2-04 to 1-06.
Keenan struck three minutes from the end for the win in what was a dour affair.
There were just five scores in the first half, Donegal leading 0-03 to 0-02 at the break.
Fermanagh’s Owen McManus scored a penalty to take the visitors ahead after the break but a lovely finish from Cian Mulligan gave Donegal the lead again.
However Keenan pounced on a defensive mistake to seal the victory.